Valve apparatus for controlling hydraulic pressure for a clutch or a brake and method for controlling hydraulic pressure

ABSTRACT

An apparatus and a method for controlling hydraulic pressure are provided, which has such advantages that a generation of peak pressure (shoot pressure ) can be lowered, mis-operation due to biting of particles can be reduced, or the cost thereof can be reduced.  
     Firstly, a large amount inflow command current is supplied to a proportional solenoid from a time point t1 to a time point t2. Consequentially, pilot pressure rises in a pilot pressure receiving chamber, so that a pressure control valve allows a large amount of hydraulic fluid to flow in a clutch or brake cylinder. At this time, potential detected by a pressure switch becomes zero level. Next, at the time point t2, a filling command small current is supplied to the proportional solenoid thereby decreasing the amount of hydraulic fluid, which flows from an input port to an output port. Such state keeps from the time point t2 to a time point t3. At the termination of filling, peak pressure may be not generated, and a speed-changing shock in a clutch may be not generated, so that smooth switching can be accomplished.

TECHNICAL FIELD

[0001] The present invention relates to a valve apparatus forcontrolling hydraulic pressure of a hydraulic pressure operated actuatorusable for a clutch or a brake, and method for controlling hydraulicpressure.

BACKGRAUND ART

[0002] A hydraulic pressure control apparatus applicable for a clutch,disclosed in Japanese Laid-Open Patent publication No. 235732/1988, willbe explained as an example of prior arts.

[0003]FIG. 9 shows a clutch cylinder 101 and a control valve 102 forcontrolling the clutch cylinder 101 in the above prior art. The controlvalve 102 includes a pressure control valve 103 for controlling clutchhydraulic pressure, and a flow rate detection valve 104. The flow ratedetection valve 104 is provided with a sensor section 105 for detectingfilling and clutch pressure level. The pressure control valve 103, theflow rate detection valve 104 and the sensor section 105 are stored inan integrated housing (107 as shown in FIG. 10). The pressure controlvalve 103 and the sensor section 105 are electrically connected to acontroller 106.

[0004] As shown in FIG. 10, the control valve 102 includes an input port110, an output port 111 and drain ports 113 and 114. To the input port110 of the control valve 102, a hydraulic fluid supply line deliveredfrom a pump (not shown) is connected. And, to the tip of the output port111, the clutch cylinder 101 (as shown in FIG. 9) is connected.

[0005] The pressure control valve 103 has a spool 115, the right end ofwhich comes in contact with a plunger 117 of a proportional solenoid. Inthe left end of the spool 115, a piston 119 is installed and a spring118 comes in contact. In the spool 115, a hydraulic chamber 120 close tothe piston 119 and a hydraulic passage 121 communicated with thehydraulic chamber 120 are formed. Hydraulic pressure in the hydraulicpassage 122 is applied, as a feedback pressure, to the hydraulic chamber120 via a hydraulic passage 121.

[0006] The flow rate detection valve 104 has a spool 125, which defineshydraulic chambers 126, 127 and 128 in the housing 107. An orifice 130is formed between the hydraulic chambers 127 and 128. Springs 131 and132 abut on the left and right ends of the spool 125, respectively. Thespool 125 is positioned at the neutral position as shown in FIG. 10under a resilient force of the springs 131 and 132 when pressure dosenot rise in the hydraulic chambers 127 and 128. When the piston 125 isat the neutral position, the hydraulic fluid, which has reached from theinput port 110 to the flow rate detection valve 104 via the hydraulicpassage 129, remains in the hydraulic chamber 126.

[0007] A detection pin 134 made of metal is disposed on the upper rightside of the flow rate detection valve 104, and the pin 134 detects thatthe spool 125 is displaced in the rightward direction from the neutralposition, as shown in FIG. 10, overcoming a resilient force of thespring 132. The detecting pin 134 is mounted to the housing 107 by acover 135 via an isolation sheet 136. From the end of the detecting pin134, a lead wire 137 is extended, which is connected to a point “a”located between resistances R1 and R2 which are connected to each otherin series. Between the resistances R1 and R2, predetermined magnitude ofDC voltage V (for instance, 12 V) is applied. The end of the resistanceR2 and the housing 107 are earthed respectively. The sensor section 105comprises these spring 132, detecting pin 134, and resistances R1 andR2.

[0008] Next, operation of the hydraulic pressure control apparatus for aclutch having the above-mentioned structure will be explained referringto FIG. 9 to FIG. 11.

[0009] The horizontal axis shows a time t in FIG. 11(A) to FIG. 11(E).The vertical axis of FIG. 11(A) shows current I commanded from thecontroller 106, the vertical axis of FIG. 11(B) shows a pump pressureP0, the vertical axis of FIG. 11(C) shows hydraulic pressure (clutchpressure) P1 in the hydraulic chamber 127 in the front of the orifice130, the vertical axis of FIG. 11(D) shows hydraulic pressure (clutchpressure) P2 in the hydraulic chamber 128 in the back of the orifice130, and the vertical axis of FIG. 11(E) shows a output S (a voltage ata point “a”) of the sensor section 105.

[0010] When a clutch will be connected, at a time point t1 in FIG. 11,the controller 106 operates so that trigger command current I1 issupplied to the proportional solenoid 116 of the control valve 102.Thereafter, the controller 106 operates so that the trigger commandcurrent I1 is lowered to an initial pressure command current I0 and suchthe condition is kept until the termination of filling. The initialpressure command current I0 corresponds to an initial pressure Pa (asshown in FIG. 11(D)) of the clutch pressure.

[0011] By supplying the trigger command current I1, the spool 115 of thepressure control valve 103 is displaced in the leftward direction sothat the input port 110 is communicated with the hydraulic passage 122.Consequentially, the hydraulic fluid delivered from the pump isintroduced from the input port 110 into the hydraulic chamber 127 of theflow rate detecting valve 104 via the hydraulic passage 122, and theninto the hydraulic chamber 128 via the orifice 130. At this moment,differential pressure (P1−P2) is generated between the hydraulicchambers 127 and 128 due to the existence of the orifice 130. Thedifferential pressure causes the spool 125 to be displaced in theleftward direction, so that the flow rate detecting valve 104 is opened.Therefore, the hydraulic fluid flows from the input port 110 into thehydraulic chamber 127 via the hydraulic passage 129 and the hydraulicchamber 126, and then into the clutch via the orifice 130, the hydraulicchamber 128 and the output port 111. The hydraulic fluid continues toflow until a clutch-back will be completely filled with it.

[0012] Here, when the spool 125 is positioned at the neutral position inFIG. 10, and, during a period in which the spool 125 is being displacedin the leftward direction from the neutral position, the spool 125 isparted away from the detecting pin 134. Accordingly, the potential atthe point “a” is a voltage V′, which is obtained by dividing the voltageV by the resistances R1 and R2, as shown in FIG. 11(E).

[0013] When the clutch-back is completely filled with the hydraulicfluid, filling will terminate. At this timing, since the hydraulic fluidstops flowing, there is no difference in pressures at the front and backof the orifice 130 (that is, P1=P2). At this moment, the spool 125 isdisplaced in the rightward direction by the spring 131 and difference inthe pressure receiving areas of the spool 125 with the result that thedetecting pin 134 is once conducted to the housing 107 earthed via thespool 125. The conduction is effected by displacement of the spool 125due to shoot pressure generated at the termination of filling. And, thespool 125 returns to the neutral position in FIG. 10 when the shootpressure disappears. Accordingly, as shown in FIG. 11(E), the potentialat the point “a” is lowered to zero at a time point t2, and rises to V′again. A detecting signal S showing the potential at the point “a” isinputted to the controller 106, which determines the termination offilling from the potential rising at point “a”. At the termination offilling, the controller 106 operates so that the command current I forthe clutch cylinder 101 is gradually increased from the initial pressurecommand current I0 (as shown in FIG. 11(A)). Incidentally, thecontroller 106 operates so that the command current for pre-stage clutchis lowered to zero at the determination of the termination of filling,as shown FIG. 11(A) with a dashed line.

[0014] As the result, the clutch pressure is lowered from the shootpressure to the initial pressure Pa and then gradually increased asshown in FIG. 11(D). Accordingly, the spool 125 is displaced in theleftward direction from the neutral position. Thereafter, when theclutch pressure is gradually increased further to exceed a set pressureTh of the spring 132 at a certain time point t3, the spool 125 isdisplaced in the rightward direction again with the result that theright end of the same comes in contact with the detecting pin 134.Therefore, at the time point t3, the potential at the point “a” islowered to zero again, and thereafter kept on such the level.

[0015] So, the potential at the point “a” becomes zero when the pressurein the clutch is higher than the set pressure Th, while the potentialbecomes a predetermined voltage when the pressure in the clutch is lessthan the set pressure. Accordingly, by monitoring the potential at thepoint “a”, it is possible to know presence or absence of the clutchpressure (that is, the engagement state of the clutch). And, in thiscase, since the potential at the point “a” rises after once beinglowered to zero, due to the shoot pressure generated at the terminationof filling, it is possible to know the termination of filling bydetecting the first rising of the shoot pressure.

[0016] However, the above-mentioned hydraulic pressure control apparatusfor a clutch has following problems.

[0017] (1) Response of the flow rate detecting valve 104 is inferior.So, as shown in FIG. 11(D), at the termination of filling, considerableshoot pressure is generated, which may cause speed changing shock.

[0018] (2) The pressure control valve 103 is driven by thrust of theplunger 117 of the proportional solenoid 116 directly. Thus, if capacityof the solenoid 116 is small, the thrust may be small, whereby amis-operation of the pressure control valve 103 may easily occur due tobiting of particles in the pressure fluid. On the other hand, when astrong solenoid is employed, the sufficient thrust can be obtained, butcauses cost-up.

[0019] In view of the above-mentioned problems, the object of thepresent invention is to provide a valve apparatus and a method forcontrolling hydraulic pressure of an actuator applicable for a clutch orbrake, which has such advantages that a generation of peak pressure(shoot pressure ) can be lowered, mis-operation due to biting ofparticles can be reduced, or the cost thereof can be reduced.

[0020] To solve the above-mentioned problems, the present inventionprovides a valve apparatus for controlling hydraulic pressure for aclutch or a brake comprises, a pressure control valve (30) having aclutch or brake cylinder inner pressure feedback chamber (31 x) at oneend thereof and a pilot pressure receiving chamber (31 y) at another endthereof, the pressure control valve introducing a clutch or brakeengagement pressure hydraulic fluid, which has brought to be flown intoa clutch or brake cylinder chamber, into the above-mentioned clutch orbrake cylinder inner pressure feedback chamber (31 x), and beingincreased the hydraulic fluid pressure of the clutch or brake engagementpressure hydraulic fluid to balance with a magnitude of pilot pressurethat is generated in the pilot pressure receiving chamber (31 y), sothat the pressure control valve (30) controls the clutch or brakecylinder pressure; a pilot fluid passage (19), through which thehydraulic fluid flows from a branched passage (18) having a throttle (26a) to the pilot pressure receiving chamber (31 y) of the above-mentionedpressure control valve (30) and drains it into a tank; a pressureproportional valve (50), which controls the pressure of the pilot fluidthat has been flown into the above-mentioned pilot pressure receivingchamber (31 y), by positioning a valve element (55) thereof at eitherposition within a drain interruption position, a throttle drain positionor a drain release position; a proportional solenoid (40), which changesthe position of the valve element (55) of the above-mentioned pressureproportional valve (50) against the flowing of the pilot fluid, andcontrols the magnitude of the pilot fluid pressure; and a pressureswitch (60), which communicates with a output port (13) of theabove-mentioned pressure control valve (30) and detects the clutch orbrake initial engagement pressure when the clutch or brake cylinderhydraulic chamber will be filled with the hydraulic fluid Since theconventional flow rate detecting valve, which is relatively inferior inresponse, is eliminated, the peak pressure (the shoot pressure) atfilling completion will not be generated. And, it is possible to reducecosts.

[0021] And, since the control is carried out by the pilot pressure, evenif the proportional solenoid has small ability, the opening size of themain passage formed at the main valve will become large, whereby a largeamount of hydraulic fluid can be flown and a operation defect of themain valve due to biting of particles will be hardly occurred.

[0022] In one aspect of the valve apparatus for controlling hydraulicpressure for a clutch or a brake according to the present invention, itis preferable that the pressure switch is such that operates when theclutch or brake cylinder hydraulic chamber is filled with the hydraulicfluid thereby rising the clutch or brake initial engagement hydraulicfluid pressure therein, and dose not operate when the pressure in theclutch or brake cylinder hydraulic chamber is less than such the initialengagement pressure.

[0023] In one aspect of the valve apparatus for controlling hydraulicpressure for a clutch or a brake according to the present invention, itis preferable that a filtering means h is provided at the upstream ofthe throttle (26 a) mounted at the pilot fluid passage (19).

[0024] In this aspect, particles can be removed by the filter therebypreventing the throttle passage from blocking.

[0025] In addition, in one aspect of the valve apparatus for controllinghydraulic pressure for a clutch or a brake according to the presentinvention, it is preferable that a second filtering means (230) isprovided outside a casing at the upstream of the above-mentionedfiltering means.

[0026] In this aspect, replacement and cleaning of the filter will beeasily carried out.

[0027] The method for controlling hydraulic pressure of the hydraulicfluid control valve, which employs the valve apparatus for controllinghydraulic fluid according to claim 1 or 2 connected to a controller,comprises following five steps.

[0028] The first step is for flowing a large amount of hydraulic fluidinto the clutch or brake cylinder hydraulic fluid chamber just beforesuch the chamber will be filled with it. In the step, a clutch or brakeengagement start command is inputted to a controller, which operates tooutput a large amount inflow command current to the proportionalsolenoid of the hydraulic fluid pressure control valve for apredetermined period. As the result, the drain of the pilot fluiddrained from the pressure proportional valve to a tank is interruptedand the pilot fluid pressure in the pilot pressure receiving chamber isincreased to a high level, so that a communicating port between theinput port and the output port of the pressure control valve becomeslarge.

[0029] The second step is for flowing a small amount of hydraulic fluidinto the clutch or brake cylinder hydraulic fluid chamber until such thechamber will be filled with it. In the step, after the predeterminedperiod in which the large amount inflow command has been outputted, thecontroller operates to output a small amount inflow command current tothe proportional solenoid of the hydraulic fluid pressure control valve.As the result, the pilot fluid is drained from the pressure proportionalvalve to a tank through a throttle and the pilot fluid pressure in thepilot pressure receiving chamber is lowered, so that the communicatingport between the input port and the output port of the pressure controlvalve becomes small.

[0030] The third step is for detecting the termination of filling. Inthe step, when the clutch or brake cylinder hydraulic fluid chamber hasbeen filled with the hydraulic fluid and the clutch or brake initialengagement pressure rises, the pressure sensor provided at the hydraulicfluid pressure control valve detects the rising of the clutch or brakeinitial engagement pressure and outputs it to the controller.

[0031] The forth step is for gradually-increasing the clutch or brakecylinder initial engagement hydraulic fluid pressure. In the step, thecontroller, which has been inputted the termination of filling, operatesto stop outputting the small amount inflow command current to theproportional solenoid of the hydraulic pressure control valve and thento supply a gradually-increasing command current to the solenoid for apredetermined period, so that the clutch or brake initial engagementhydraulic fluid pressure reaches a set pressure for such thepredetermined period. As the result, the opening size of the throttle,through which the pilot fluid is drained from the pressure proportionalvalve to the tank, is gradually decreased to allow the pilot fluidpressure in the pilot pressure receiving chamber to be graduallyincreased, and the pressure in the clutch or brake cylinder innerpressure feedback chamber of the pressure control valve to be increasedto balance with such the gradually-increased pilot fluid pressure.

[0032] The fifth step is for outputting the set pressure command signalto the proportional solenoid of the hydraulic fluid pressure controlvalve. In the step, after such the predetermined period in which theclutch or brake initial engagement hydraulic fluid pressure is beingincreased, the controller operates to stop the hydraulic fluid pressuregradually-increasing command current, and to keep the clutch or brakeengagement set pressure, in which the gradually-increasing of thepressure has been finished.

BRIEF DESCRIPTION OF THE DRAWING

[0033]FIG. 1 is a sectional drawing showing a clutch hydraulic pressurecontrol apparatus according to the first embodiment of the presentinvention at a drain state.

[0034]FIG. 2 is a sectional drawing showing the same apparatus as FIG. 1at an operating state.

[0035]FIG. 3 is a sectional drawing showing the same apparatus as FIG. 1at a pressure adjusting.

[0036]FIG. 4 is a graph between command current and, clutch pressure andpilot pressure, in the same apparatus as FIG. 1.

[0037]FIG. 5 is a timing chart showing an operation of the sameapparatus as FIG. 1.

[0038]FIG. 6 is a sectional drawing showing a clutch hydraulic pressurecontrol apparatus according to the second embodiment of the presentinvention.

[0039]FIG. 7 is a circuit diagram showing a clutch hydraulic pressurecontrol apparatus according to the embodiment of the present invention.

[0040]FIG. 8 is a sectional drawing showing a clutch hydraulic pressurecontrol apparatus according to the third embodiment of the presentinvention.

[0041]FIG. 9 is a circuit diagram showing a hydraulic pressure circuitof a clutch hydraulic pressure control apparatus according to theconventional apparatus.

[0042]FIG. 10 is a sectional drawing showing a structure of the valve inthe same apparatus as FIG. 9.

[0043]FIG. 11 is a timing chart showing the operation of the sameapparatus as FIG. 9.

DETAILED DESCRIPTION OF THE INENTION

[0044] In the following, specific examples of the present invention willbe explained referring to the drawings. Here, in the followingexplanation, the upper and lower, and the left and right mean thedirection in the respective drawings.

[0045] {The First Embodiment}

[0046] As shown in FIGS. 1 to 3, a clutch hydraulic pressure controlapparatus 1 according to the first embodiment of the invention has ahousing 3, in which are provided an input port 11 communicated with apump, an output port 13 communicated with a clutch cylinder, and drainports 15 and 17 communicated with a tank. In addition, in the housing 3,a pilot pressure receiving chamber 19 is formed between the drain ports15 and 17. The pilot pressure receiving chamber 19 and the input port 11is communicated each other via a passage 16 and a pilot pressure supplypassage 18.

[0047] Among them, the input port 11 and the output port 13 defines amain passage extended from the pump to the cylinder.

[0048] At the passage 16 between the input port 11 and the pilotpressure supply passage 18, a screw 26 is disposed. At the right end ofthe screw 26, is formed a male screw 26 b, which is screwed to an innersurface of the pilot pressure supply passage 18. Between the left end ofthe screw 26 and the inner wall of the passage 16, a clearance h isdefined. The clearance h acts as a filter for preventing a throttlepassage 26 a from blocking. In the screw 26, the throttle passage (thefirst throttle passage) 26 a is formed, which communicates the passage16 with the pilot pressure supply passage 18. The screw 26 can beattached or detached through a screw bore 3B formed at the housing 3thus enabling replacement and cleaning of the filter. Here, the screwbore 3B is generally closed by a plug 3X.

[0049] In the housing 3, a pressure control valve 30, a pressureproportional valve 50 and a proportional solenoid 40 are provided.

[0050] In the housing 3, the pressure control valve 30 is slidablydisposed, which has a left end section 31 a, a right end section 31 band a center section 31 c between the end sections 31 a and 31 b. Afeedback chamber 31X of clutch or brake inner pressure is formed at theleft end section 31 a, while a pilot pressure receiving chamber 31 y isformed at the right end section 31 b.

[0051] At the center section 31 c, a feedback passage 31 z is formed,which communicates the output port 13 with the clutch or brake innerpressure feedback chamber 31 x. In the clutch or brake inner pressurefeedback chamber 31 x of the pressure control valve 30, a spring 33 isinstalled. At a closed state (the proportional solenoid 30 is notexcited), as shown in FIG. 1, the spring 33 causes the pressure controlvalve 30 to be displaced in the rightward direction under the resilientforce thereof, thereby interrupting the communication between the inputport 11 and output port 13 and communicating the output port 13 with thedrain port 17. As the result, the hydraulic fluid dose not flow into theclutch or brake and is drained from the clutch or brake, so that theclutch or brake is to become a non acting state.

[0052] At an acting state (the proportional solenoid 30 is excited), asshown in FIG. 2, the spring 33 is compressed by pressure generated inthe pilot pressure receiving chamber 31 y to cause the pressure controlvalve to be displaced in the leftward direction thereby communicatingthe input port 11 with the output port 13 and interrupting thecommunication between the output port 13 and the drain port 17. As theresult, the hydraulic fluid is introduced into the clutch or brake, sothat the clutch or brake will be switched to the acting state.

[0053] Next, the pressure proportional valve 50 will be explained.

[0054] The pressure proportional valve 50 has a valve seat body 50 xscrewed to a connecting section 41 of the proportional solenoid 40 byscrews, and a valve element 55.

[0055] The valve seat body 50 x comprises a section facing to the pilotpressure receiving chamber 31 y in the housing 3, a female screw section41 screwed to the connecting section 41 of the proportional solenoid 40,axial drain passages 51 c and 51 b and a radial drain passage 51 athrough which the hydraulic fluid in the pilot pressure receivingchamber 31 y is drained, a valve element seat surface 51 d formed at theposition where the axial drain passages 51 c and 51 b are communicatedwith the radial drain passage 51 a, and a container in which the valveelement 55 is removably supported.

[0056] The valve element 55 comes in contact with the valve element seatsurface 51 d, and is so disposed in the container in the valve seat body50 x that it can be displaced between a position where the communicationbetween the axial drain passage 51 b and the radial drain passage 51 ais interrupted, and a position where it is possible to change the amountof the drain fluid. With such the construction, the valve element 55 canbe displaced within a clearance between the valve element seat surface51 d and itself by flowing of the drain fluid and operation of theproportional solenoid 40.

[0057] A pilot pressure circuit is constructed by the above-mentionedinput port 11, the passage 16, the throttle passage 26 a, the pilotpressure supply passage 18, the pilot pressure receiving chamber 31 y,the axial drain passage 51 b, the radial drain passage 51 a, the valveelement 55, the valve element seat surface 51 d and the drain port 17.

[0058] Next, the proportional solenoid 40 will be explained.

[0059] The proportional solenoid 40 is attached to the inside of thehousing by screws from the outside of the housing. The proportionalsolenoid 40 has a main body 43 and a connecting section 41 protrudingfrom the main body 43. The connecting section 41 is sleeve-shaped andhas a flange 41 c. On the inner and outer surfaces of the left endsection of the connecting section 41, a female screw 41 a and a malescrew 41 b are formed respectively. The female screw 41 a screws andsupports the pressure proportional valve 50, while the male screw 41 bis screwed in a screw bore 3A of the housing 3. With such theconstruction, the proportional solenoid 40 is supported to the housing3. An O-ring 44 seals between the opening edge of the screw bore 3A andthe flange 41 c of the connecting section 41.

[0060] The proportional solenoid 40 has a shaft 47 at its axis center,which can be displaced in the leftward or rightward direction underexcitation of a coil (not shown) in the main body 43. When the shaft 47is displaced in the leftward direction, the valve element 55, whichcomes into contact with the tip of the shaft 47, is pressed to the valveelement seat surface 51 d to close the axial drain passage 51 b, so thatthe valve element 55 cannot be displaced. When the shaft 47 is displacedin the rightward direction, the valve element 55 will be able to bedisplaced whereby a clearance is defined between the valve element 55and the valve element seat surface 51 d. Therefore, due to such theclearance, the axial drain passage 51 b is opened, so that the hydraulicfluid is drained from the pilot pressure receiving chamber 31 y. Theproportional solenoid 40 is connected to the controller (not shown),which operettas to control current applied to the proportional solenoid,that is, a displacement position of the shaft 47 or press force of thevalve element 55 is controlled.

[0061] Next, the pressure switch 60 provided at the upper side of theinside of the housing 3 will be explained.

[0062] At the upper portion of the housing 3, a chamber 21 is formed, inwhich a spool 70 that constructs the pressure switch 60 is disposed. Inthe housing 3, a pressure detecting passage 23 is formed between thechamber 21 and the output port 13. In addition, the chamber 21 iscommunicated with the drain port 17.

[0063] The spool 70 of the pressure switch 60 is constructed by a leftspool 71 and a right spool 73 which are fitted each other with a recessand a protrusion coupling. In the center of the spool 70, a piston 75 isslidably built. In the left spool 71, is defined a hollow part 71 a, inwhich a spring 72 is displaced. The right end of the spring 72 comes incontact with the flange 75 a of the piston 75 to bias the piston 75rightward. To the right spool 73, a spring 74 is surrounded, the leftend of which comes in contact with a flange 73 a of the right spool 73to bias the right spool 73 leftward.

[0064] The pressure switch 60 has an attachment 65 and a bellows-shapedcover 62 combining with an isolation sheet 67. The attachment 65 isfixed to the housing 63 by a bolt 68. An O-ring 69 seals between theattachment 65 and the opening edge of the chamber 21 in the housing 3.On the isolation sheet 67, a switch bar 61 made of metal is supported.The left end of the switch bar 61 dose not come in contact with the tipof the piston 75, while the right end of the switch bar 61 is connectedto a same detecting circuit as that of the apparatus as described inFIG. 10. As the spool 70 is pressed by the hydraulic pressure in theoutput port 13, the spring 74 is compressed and displaced in therightward to bring the piston 75 to come in contact with the switch bar61. This causes the passage extended from the output port 13 to theinside of the clutch to be filled with the hydraulic fluid whereby aclutch or brake initial engagement pressure rises. The rising of thepressure will be detected by the detecting circuit. The spring 74 has aintensity such that, when the hydraulic pressure in the passage extendedfrom the output port 13 to the inside of the clutch will be more thanthe clutch or brake initial engagement pressure, the spring 74 is socompressed that the piston 75 can be displaced in the pressure detectingdirection, and, when less than the clutch or brake initial engagementpressure, it cannot be displaced in the pressure detecting direction.The signal outputted from the detecting circuit is sent to thecontroller. The switch bar 61 is covered with the bellows-shaped cover62.

[0065] Next, the operation of the hydraulic pressure control apparatus 1having the above-mentioned construction will be explained referring toFIGS. 1 to 5.

[0066] In FIG. 5(A) to FIG. 5(B), the qardrature axis shows a time t.The vertical axis shows a command current I outputted from thecontroller (that is, press force of the proportional solenoid 40) inFIG. 11(A), pressure PP in the pilot pressure chamber in FIG. 11(B),clutch pressure PK in FIG. 11(C), and a potential V detected by thepressure sensor 60 in FIG. 11(D).

[0067] First, at a non engagement state of a clutch or brake, current isnot supplied to the proportional solenoid 40. At this time, the shaft 47is displaced in the rightward direction, so that the valve element 55,which comes in contact with the tip of the shaft 47, is pressed by thepilot fluid in the pilot pressure receiving chamber 31 y to be partedaway from the valve element seat surface 51 d with the result that aclearance is defined between the valve element seat surface 51 d anditself. Therefore, the hydraulic fluid delivered from a pump isintroduced from the input port 11 to the drain port 17, via the passage16, a throttle passage 26 a of the screw 26, the pilot pressure supplypassage 18, the pilot pressure receiving chamber 19, the axial drainpassages 51 c and 51 b of the pressure proportional valve 50 and theradial drain passage 51 a of the same.

[0068] At this moment, since the pressure in the pilot pressurereceiving chamber 19 becomes substantially equal to that in the drainport 17, pilot pressure dose not rise in the pilot pressure receivingchamber 19. Therefore, the pressure control valve 30 is displaced in therightward direction under a resilient force of the spring 33 and comesin contact with the valve seat body 50 x of the pressure proportionalvalve 50 thereby being positioned. And, since the input port 11 is notcommunicated with the output port 13 and the output port 13 iscommunicated with the drain port 15, the hydraulic pressure is notsupplied to the clutch cylinder.

[0069] In such a state in which the clutch will be connected from nonengagement state, as shown in FIG. 5(A), at a time point t1, thecontroller operates to supply a large amount flow-in command current tothe proportional solenoid in order to excite the proportional solenoid40. The excitation is kept until a time point t2 (for instance, about0.1 second).

[0070] The excitation of the proportional solenoid 40 allows the shaft47 to be displaced in the leftward direction from the position as shownin FIG. 1 with a force in proportion to the supplied current, so thatthe valve element 55, which comes in contact with the tip of the shaft47, is pressed to the valve element seat surface 51 d to close the axialdrain passage 51 b. Accordingly, the pilot pressure receiving chamber 19is isolated from the drain port 17 with the result that pilot pressurerises in the pilot pressure receiving chamber 19 as shown in FIG. 5(B).Such the pilot pressure is proportion to the excitation force, which isproduced by supplying the large amount command current to theproportional solenoid 40, and is larger than the resilient force of thespring 33, so that the pressure control valve 30 is displaced in theleftward direction to allow the pilot pressure circuit to become aopened state as shown in FIG. 2.

[0071] As shown in FIG. 2, as the pressure control valve 30 is displacedin the leftward direction, the input port 11 is communicated with theoutput port 13 and the communication between the output port 13 and thedrain port 17 is interrupted. Such the state is being kept during aperiod from the time point t1 to the time point t2, at which thepressure control valve 30 is almost full-opened, so that a large amountof hydraulic fluid is flown into the clutch or brake chamber in a shortperiod just before the clutch or brake chamber will be completely filledwith the hydraulic fluid. At the period between the time point t1 andthe time point t2, the clutch pressure will be larger than the initialengagement hydraulic fluid pressure as the clutch or brake chamber hasbeen completely filled with the hydraulic fluid, as shown in FIG. 5(c).

[0072] At this moment, pressure rises in the pressure detecting passage23 to cause the spool 70 of the pressure switch 60 to be displaced inthe rightward direction overcoming the bias force of the spring 74.Accordingly, the piston 75 is pressed to the switch bar 61, wherebypotential detected by the pressure switch 60 becomes zero level.

[0073] Next, at the time point t2, as shown in FIG. 5(A), the controlleroperates to switch the command current I to a filling command smallcurrent I2, which is lowered in order to flow the hydraulic fluid intothe clutch or brake chamber in a pressure which is so controlled as toexceed the clutch or brake initial engagement hydraulic fluid pressure alittle, and keep such the state until the termination of filling. Sincethe command current is lowered, the excitation force of the proportionalsolenoid 40, by which the valve element 55, which comes in contact withthe tip of the shaft 47, is pressed to the valve element seat surface 51d, is switched to an exciting force in proportion to the loweredcurrent. Therefore, the pilot pressure in the pilot pressure receivingchamber 31 y causes the valve element 55, which closes the drainpassage, to be displaced with the result that a clearance is definedbetween the valve element 55 and the valve element seat surface 51 d,whereby the pilot fluid in the pilot pressure receiving chamber 31 y isdrained through such the clearance. In the drain of the pilot fluid, theclearance between the valve element 55 and the valve element seatsurface 51 d is so controlled that the pressure in the pilot pressurereceiving chamber 31 y will be kept in proportion to the excitationforce in response to the above-mentioned filling command small currentI2. And, the pressure control valve 30 is moved back by the pressure inthe feedback pressure receiving chamber 31 x in the clutch or brakechamber to be displaced in the rightward direction.

[0074] The displacement of the pressure control valve 30 in therightward direction causes the output port 13 to be communicated withthe drain port 15 and the hydraulic fluid in the clutch or brake chamberto be drained, so that the pressure in the feedback pressure receivingchamber 31 x is lowered. The lowering of the pressure keeps until thepressure in the feedback pressure receiving chamber 31 x will bebalanced with the hydraulic fluid pressure in the pilot pressurereceiving chamber 31 y, which is proportion to the excitation forceproduced by supplying the above-mentioned filling command current. Atthe moment, the communication between the output port 13 and the drainport 15 is interrupted and the communication opening between the inputport 11 and the output port 13 is throttled, so that the amount of thehydraulic fluid which flows into the output port 13 becomes small. Asthe result, the clutch or brake chamber, which is not completely filledyet, will be completely filled by supplement of the small amount ofhydraulic fluid and the clutch or brake will be engaged without beingshocked. The operation is kept until the clutch or brake chamber will becompletely filled with the hydraulic fluid.

[0075] During a period in which a small amount of hydraulic fluid isbeing flown for supplement, since the clutch or brake chamber is notfilled with the hydraulic fluid, the spring 72 of the pressure switch 60biases the spool 70 in the leftward direction whereby the pressureswitch 60 dose not operates. Therefore, the piston 75 is parted from theswitch bar 61 whereby potential detected by the pressure switch 60increases (for instance, 24V), as shown in FIG. 5(D).

[0076] Such flowing of a small amount of hydraulic fluid for supplementis kept until the pressure switch 60 will detect that filling of theactuator chamber with the hydraulic fluid has terminated. At this time,since the clutch or brake chamber will be completely filled with thehydraulic fluid and the clutch or brake initial engagement hydraulicfluid pressure rises, the spring 72 of the pressure switch 60 iscompressed by the initial pressure to causes the spool 70 to bedisplaced in the rightward direction, whereby the pressure switch 60begins to operate.

[0077] Here, as shown in FIG. 5(D), the pressure switch 60 detects afirst high output pressure (the voltage is 0 level) at the time point t1(when the valve is opened), a low output pressure (the voltage is 24V)at the time point t2 (when the valve is throttled), and thereafter asecond high output pressure (the voltage is 0 level) at the terminationof filling (the time point t3). During such the period, the controlleroperates to cancel the first high output pressure and detect thetermination of filling by the second high output pressure. Thecontroller, which has received the second detecting signal showing thetermination of filling, operates so that the command current I isswitched from the filling command small electrical current I2 to ahydraulic fluid pressure gradually-increasing command current forapplying a gradually-increasing excitation force to the coil in theproportional solenoid 40, as shown in FIG. 5(A). Here, the seconddetecting signal at the termination of filling may take as a timeguideline in which the actuator chamber comes to be filled with thehydraulic fluid initially. Accordingly, in a case in which the apparatusaccording to the present invention will applied to a speed-changingclutch, when a initial filling period may be over a predetermined periodby abrasion of a clutch lining, or, when inflow amount of the hydraulicfluid, with which a clutch cylinder is filled, will be changed byslowness and fastness of the flow speed of the hydraulic fluid relatedto engine rotational frequency and temperature of the fluid, resultingin the initial filling period being over or below the predeterminedperiod, the apparatus controls the period at which the large amountinflow command is outputted. Accordingly, the inflow amount of thehydraulic fluid can be regulated so that the period, in which theactuator chamber comes to be filled with the hydraulic fluid initially,can be suitably adjusted in order to correct a clutch engagement period.

[0078] The gradually-increasing excitation of the proportional solenoid40 causes the shaft 47 to be displaced in the leftward directiongradually, in FIG. 1, with the result that the clearance between thevalve element 55, which comes in contact with the tip of the shaft 47,and the valve element seat surface 51 d is gradually narrowed againstthe flowing of the pilot fluid. Thus, since the amount of hydraulicfluid decreases, which escapes from the pilot pressure receiving chamber19 to the drain port 17 via the axial drain passages 51 c and 51 d andthe radial drain passage 51 a, the hydraulic fluid pressure in the pilotpressure receiving chamber 19 will increase in proportion to thegradually-increasing current applied to the proportional solenoid 40, asshown in FIG. 5(B).

[0079] As the result, the hydraulic fluid pressure in the pilot pressurereceiving chamber 19 will gradually increase, by which the communicationbetween the output port 13 and the drain port 17 keeps to beinterrupted. Therefore, the controller operates to adjust thegradually-increasing of the clutch or brake engagement hydraulic fluidpressure so that the communication between the input port 11 and theoutput port 13 is kept to cause the hydraulic fluid to be flown into theclutch chamber in order to increase the pressure in the feedbackpressure receiving chamber 31 x in balance with the gradually-increasingpressure produced in the pilot pressure receiving chamber 19.

[0080] Such the gradually-increasing control of the clutch or brakeengagement hydraulic fluid pressure is carried out as the followings.Firstly, the controller operates to output a gradually-increasingcommand current to the proportional solenoid 40 for a predeterminedperiod, so that the clutch or brake engagement hydraulic fluid pressurewill be increased to the set pressure for the predetermined period.After such the predetermined period, the controller operates to switchthe gradually-increasing command current to a clutch or brake engagementpressure set command current, so that the pressure in the pilot pressurereceiving chamber 19 is kept constant. And, when the pressure in theclutch or brake feedback chamber 14 exceeds the pressure in the pilotpressure receiving chamber 19, the communication between the output port13 and the drain port 15 or the input port 11 of the pressure controlvalve 30 respectively is intermittently interrupted, so that thepressure in the clutch or brake feedback chamber 14 will be balancedwith the pressure in the pilot pressure receiving chamber 19 in order tokeep the clutch or brake engagement set pressure constant. Incidentally,the predetermined gradually-increasing period, from a time point whenthe second filling signal is detected by the pressure switch 60 to atime point when the pressure in the pilot pressure receiving chamber 19reaches the clutch or brake engagement set pressure, will be socontrolled that a period until an engagement of a clutch or brake willbe variable, by shortening or extending of the engagement period, orchanging the gradually-increasing current in the predetermined period inwhich the gradually-increasing current command is being outputted, inresponse to the clutch or brake engagement condition(for instance, whena vehicle runs a upgrade or a downgrade, or level way).

[0081] The valve apparatus for controlling hydraulic pressure has theabove-mentioned structure will have effects described followings. In theconventional apparatus, when a clutch cylinder is completely filled witha hydraulic fluid, a difference in the pressure receiving areas of thefront and back of a throttle causes a flow rate detecting valve to bedisplaced and come in contact with a filling detecting probe. In thiscase, since the detecting probe is displaced after the termination offilling, responsibility in the apparatus is so bad that shoot pressuremay be generated, which causes an engagement shock of the clutch.However, in this apparatus according to the present invention, thedetecting probe is constructed such that, when a clutch or brakecylinder is completely filled with a hydraulic fluid and a clutch orbrake initial engagement pressure rises, detection will be carried out,and, during a period in which the cylinder is being filled with thehydraulic fluid under the initial pressure, detection will not becarried out. Accordingly, it is possible to have good response andprevent occurrence of the shoot pressure in comparison with theconventional method for being displaced the detecting prove bydifference in the pressure receiving areas.

[0082] Furthermore, since the pressure control valve is controlled to bedisplaced by the pilot pressure, displacing force and displacementstroke will be improved in comparison with the conventional displacementcontrol by magnetic force of the proportional solenoid. Accordingly,occurrence of displacement stick is prevented and a large amount ofhydraulic fluid can be flown, and it is not necessary to use theproportional solenoid having a large exciting force, whereby it is ableto possible to reduce costs.

[0083] {The Second Embodiment}

[0084] Referring FIG. 6 and FIG. 7, a second embodiment according to thepresent invention will be explained.

[0085] In a clutch hydraulic pressure control apparatus 201 as shown inFIG. 6, main difference from that of the first embodiment as shown inFIG. 1 to FIG. 3 is the structure of the housing thereof. A pressurecontrol valve 30, a pressure proportional valve 50, a proportionalsolenoid 40 and a pressure switch 60 has similar structure and functionas that of the first embodiment respectively.

[0086] As shown in FIG. 6, in a housing 203 of the clutch hydraulicpressure control apparatus 201 according to the second embodiment, ainput port 211 communicated with a pump, a output port 213 communicatedwith a clutch cylinder, and drain ports 215 and 217 communicated with atank respectively are provided.

[0087] Among them, a main passage from the pump to the cylinder isconstituted by the input port 211 and the output port 213.

[0088] In the housing 203, at the right of the drain port 215, a pilotpressure receiving chamber 219 is defined, in which a right end section31 b of the pressure control valve 30 is slidably disposed. To the upperside of the pilot pressure receiving chamber 219, is communicated apilot pressure supply passage 218, which is communicated with an outputpassage of the pump via a filter h and a throttle 216.

[0089] An outside attached filter 230 in FIG. 6 acts as a pilot fluidfilter, when a pilot fluid is delivered from the input port 211 of thepump and flowed into the apparatus. The outside attached filter 230 isso disposed outside the housing 203 that it is easy to carry out amaintenance. The filter h in FIG. 7 acts as a filter which prevents thethrottle 26 a from blocking in the first embodiment from blocking in thefirst embodiment.

[0090] At the upper of the housing 203, a chamber 221 is defined, inwhich the spool 70 that constructs the pressure switch 60 is disposed.In the housing 203, a pressure detecting passage 223 is defined betweenthe chamber 221 and the output port 213. And, the chamber 221 is alsocommunicated with the drain port 217.

[0091] In the clutch hydraulic pressure control apparatus 201 of thesecond embodiment, the peak pressure (the shoot pressure) at thetermination of filling, which usually occurs in the conventionalapparatus, dose not occur, because it is controlled in the same manneras the clutch hydraulic pressure control apparatus 1 in the firstembodiment. Accordingly, a speed-changing shock in a clutch may be notgenerated, so that smooth switching can be accomplished. Especially, insuch the clutch hydraulic pressure control apparatus 201, since theoutside attachment filter 230 is positioned outside the housing 203, itis easy to carry out a maintenance.

[0092] {The Third Embodiment}

[0093] Referring FIG. 8, a third embodiment according to the presentinvention will be explained.

[0094] The main feature of a clutch hydraulic pressure control apparatusin the third embodiment is such that a pilot pressure supply passage isdefined in a pressure control valve.

[0095] The clutch hydraulic pressure control apparatus 301 as shown inFIG. 8 has a housing 303, in which are provided a input port 311communicated with a pump, a output port 313 communicated with a clutchcylinder and a drain port 315 communicated with a tank.

[0096] A pressure control valve 330, a pressure proportional valve 350and a proportional solenoid 340 are aligned in an axial line from theinside to the outside of the housing 3.

[0097] Firstly, the pressure control valve 330 will be explained.

[0098] The pressure control valve 330 has a land section 334C, whichseparates the input port 311 from the output port 313 and slides in theleft and right directions to be selectively communicated between theinput port 311 and the output port, a land section 313A, which separatesthe output port 313 from the drain port 315 and slides in the left andright directions to be selectively communicated between the output port313 and the drain port 315, a land section 334B, which interrupts thecommunication with the input port 311, and the end surface of whichaffects as a pressure receiving surface 380 for the pilot fluid, and aland section 332B which receives a resilient force of a spring 333.

[0099] In addition, the diameter of the land section 334C becomes solarger than that of the land section 313A that a circular pressurereceiving surface 332D is defined, which affects as a feedback pressurereceiving surface for clutch or brake engagement pressure. Additionally,at a small diameter section defined between the land section 323 and theland section 334B, a radial passage is formed. Further, an inside axialpassage 334 a is formed, which has a throttle passing passage 326 a thatcommunicates with the radial passage and reaches the end surface 380 ofthe land section 334B. With such the construction, a pilot fluid canload on the end surface of the pressure control valve 330.

[0100] And, the diameter of the land section 313A becomes equal to thatof the land section 332B, and a circular groove 332C is formed betweenthe land sections 313A and 332B. In addition, an axial passage 332 b isformed at the outer surface of the land section 332B, with the resultthat the circular groove 332C is to be communicated with the axialpassage 332 b, which affects as a drain passage communicating betweenthe input port 313 and the output port 315.

[0101] Next, the pressure proportional valve 350 will be explained.

[0102] The pressure proportional valve 350 has a cylindrical valve seatbody 352, which is aligned and close to the pressure control valve 330.In the cylindrical valve seat body 352, a pilot fluid chamber 352 a, athrottle drain 352 b in the pilot fluid chamber 352 a, a trombone-shapedvalve seat 352 d and a pilot fluid drain 354 in the pilot fluid chamber352 a are aligned on the axis thereof. The pilot fluid chamber 352 bfaces an inner axial passage 334 a opened to the pilot fluid pressurereceiving end surface 380 of the pressure control valve 330. Force ofthe valve element 355, which is pressed against the trombone-shapedvalve seat 352 d by the shaft 347 of the proportional solenoid 340, isso adjusted that the flow amount of the drain fluid from the throttledrain 352 b can be controlled.

[0103] A drain section 354 is located in a drain chamber 381 in thehousing 303. In the drain section 354, a drain fluid passage 354 acommunicated with the inside of the drain chamber 381 is formed. At theright end of the drain section 354, an engagement flange section 356 isformed, which is engaged with a stepped section formed between the drainchamber 381 and a spot facing 383. At the axis center of the drainsection 354, a center hole 354 b is formed.

[0104] Next, the proportional solenoid 340 will be explained.

[0105] The proportional solenoid 340 has the almost same structure asthe proportional solenoid 40 in the above-mentioned first and secondembodiments substantially. However, the structure of the connectingsection is different a little.

[0106] The proportional solenoid 340 has a connecting section 341, whichis sleeve-shaped. At the left end of the connecting section 341, acircular bias section 342 is formed. On the outside of the connectingsection 341, an attachment plate 346 is provided. The proportionalsolenoid 340 is fixed to the attachment plate 346 provided at the rightend surface of the housing 303. In such the fixed state, the biassection 342 of the connecting section 341 comes in contact with theright end surface of the engagement flange section 356 of the pressureproportional valve 350, therefore, the pressure proportional valve 350is fixed to the inside of the housing 303. Incidentally, the shaft 347of the proportional solenoid 340 has the almost same structure as thatof the proportional solenoid 40 in the above-mentioned first and secondembodiments.

[0107] At the upper portion of the housing 303, a chamber 221 is formed,in which a spool 70 that constructs the pressure switch 60 is disposed.In the housing 303, a pressure detecting passage 323 is formed betweenthe chamber 221 and the output port 313. The chamber 221 is communicatedwith the drain port 315.

[0108] In the clutch hydraulic pressure control apparatus 301 in thethird embodiment, in the closed state, the shaft 347 of the proportionalsolenoid 340 is displaced in the rightward direction so that a clearanceis defined between the valve element 355 which comes in contact with thetip of the shaft 347, and the valve element seat surface 352 d of thevalve seat body 350. At this time, the hydraulic fluid delivered frompump is introduced from the input port 313, and flows to the hydraulicfluid passage 334 a formed at the large diameter section 334 of thepressure control valve 330 (containing the hydraulic fluid passage 326 aformed at the orifice section 326), to the hydraulic fluid passage 352 aformed at the valve seat body 350 (containing the throttle passage 352b) to the drain fluid passage 354 a and finally to the drain port 317.At the moment, since pilot pressure will not rise between the pressurecontrol valve 330 and the valve seat body 350(the right chamber 380,that is, a pilot pressure receiving chamber), the pressure control valve330 is displaced in the rightward direction under the bias force of thespring 333 and comes in contact with the valve seat body 350.Accordingly, as shown in FIG. 8, the communication between the inputport 311 and the output port 313 is interrupted by the left largediameter section 334C, and the output port 313 is communicated with thedrain port 315, so that hydraulic pressure is not applied to the clutchcylinder.

[0109] When the clutch will be connected, the proportional solenoid 340is excited as to displace the shaft 347 in the left direction, so thatthe valve element 355 is pressed onto the valve element seat surface 352d and closes the throttle passage 352 b. Consequently, the hydraulicfluid delivered from the pump is introduced from the input port 311, andflows to the hydraulic fluid passage 334 a formed at the large diametersection 334 of the pressure control valve 330 (containing the hydraulicfluid passage 326 a formed at the orifice section 326), and to thehydraulic fluid passage 352 a of the valve seat body 350(containing thethrottle passage 352 b). As the result, pressure rises in the rightchamber 380 located between the pressure control valve 330 and the valveseat body 350. When the pilot pressure will be larger than the biasforce of the spring 333, the pressure control valve 330 is displaced inthe leftward direction.

[0110] As the pressure control valve 330 is displaced in the leftwarddirection, the left large diameter section 334C of the pressure controlvalve 301 is to be positioned in the output port 313, with the resultthat the communication passage 312 is opened, whereby the input port 311is communicated with the output port 313. Therefore, the hydraulic fluidis introduced into the clutch cylinder to cause the clutch pressure tobe increased. Next, as the command current supplied to the proportionalsolenoid 340 is decreased, the shaft 347 is displaced in the rightwarddirection a little, whereby the press force to the valve element seatsurface 352 d of the valve element 355 weakens. Consequently, thehydraulic fluid delivered from the input port 311 is introduced from thehydraulic fluid passage 334 a formed at the large diameter section 334of the pressure control valve 330 (containing the hydraulic fluidpassage 326 a formed at the orifice section 326) and flows to thehydraulic fluid passage 352 a formed at the valve seat body 350(containing the throttle passage 352 b), to the drain fluid passage 354a, and finally to the drain port 317. As the result, the pressurecontrol valve 330 is displaced in the right direction, so that theopening of the communication passage 312 decreases, whereby the amountof hydraulic fluid introduced from the input port 11 to the output port13 becomes small.

[0111] As described above, in the third embodiment, the flowingdirection of the hydraulic fluid is different from that of theabove-mentioned first and second embodiments. However, since control ofthe hydraulic fluid is carried out as the same manner as theabove-mentioned manner, pressure regulation and modulation will becarried out as the same manner. Accordingly, in the third embodiment,the peak pressure (the shoot pressure) at the termination of filling,which occurs conventionally, is not generated.

[0112] Especially, in the third embodiment, since the orifice section326 is provided in the hydraulic fluid passage 334 a in the pressurecontrol valve 301, the housing 303 has become compact. Accordingly, theapparatus can be installed in a small space.

EFFECTS OF THE INVENTION

[0113] As mentioned above, the present invention has following effects.

[0114] (1) The peak pressure (the shoot pressure) is not generated,which occurs at the termination of filling in the conventionalapparatus. And, it is possible to reduce costs.

[0115] (2) A large amount of hydraulic fluid can be flown.

[0116] (3) Even if the proportional solenoid has small capacity, themis-operation due to biting of particles hardly occurs. In addition,because the solenoid may have small thrust, it is possible to reducecosts.

[0117] (4) In the case in which a filter is disposed at the upstream ofa throttle, the filter can prevent the throttle passage from blocking.

[0118] (5) In the case in which a filter is disposed outside the casing,replacement and cleaning of the filter easily carried out.

We claim:
 1. Valve apparatus for controlling hydraulic pressure for aclutch or a brake comprises, a pressure control valve (30) having aclutch or brake cylinder inner pressure feedback chamber (31 x) at oneend thereof and a pilot pressure receiving chamber (31 y) at another endthereof, the pressure control valve introducing a clutch or brakeengagement pressure hydraulic fluid, which has brought to be flown intoa clutch or brake cylinder chamber, into the above-mentioned clutch orbrake cylinder inner pressure feedback chamber (31 x), and beingincreased the hydraulic fluid pressure of the clutch or brake engagementpressure hydraulic fluid to balance with a magnitude of pilot pressurethat is generated in the pilot pressure receiving chamber (31 y), sothat the pressure control valve (30) controls the clutch or brakecylinder pressure; a pilot fluid passage (19), through which thehydraulic fluid flows from a branched passage (18) having a throttle (26a) to the pilot pressure receiving chamber (31 y) of the above-mentionedpressure control valve (30) and drains it into a tank; a pressureproportional valve (50), which controls the pressure of the pilot fluidthat has been flown into the above-mentioned pilot pressure receivingchamber (31 y), by positioning a valve element (55) thereof at eitherposition within a drain interruption position, a throttle drain positionor a drain release position; a proportional solenoid (40), which changesthe position of the valve element (55) of the above-mentioned pressureproportional valve (50) against the flowing of the pilot fluid, andcontrols the magnitude of the pilot fluid pressure; and a pressureswitch (60), which communicates with a output port (13) of theabove-mentioned pressure control valve (30) and detects the clutch orbrake initial engagement pressure when the clutch or brake cylinderhydraulic chamber will be filled with the hydraulic fluid.
 2. The valveapparatus for controlling hydraulic pressure for a clutch or a brakeaccording to claim 1, wherein the pressure switch is such that operateswhen the clutch or brake cylinder hydraulic chamber is filled with thehydraulic fluid whereby the clutch or brake initial engagement hydraulicfluid pressure rises therein, and dose not operate when the pressure inthe clutch or brake cylinder hydraulic chamber is less than such theinitial engagement hydraulic fluid pressure.
 3. The valve apparatus forcontrolling a hydraulic pressure for a clutch or a brake according toclaim 1 or claim 2, wherein a filtering means h is provided at theupstream of the throttle (26 a) mounted at the pilot fluid passage (19).4. The valve apparatus for controlling a hydraulic pressure usable for aclutch or a brake according to claim 3, wherein a second filtering means(230) is provided outside a casing at the upstream of theabove-mentioned filtering means.
 5. The method for controlling hydraulicpressure of the hydraulic fluid control valve, which employs the valveapparatus for controlling the hydraulic fluid according to claim 1 or 2connected to a controller, comprises five steps, the first step forflowing a large amount of hydraulic fluid into the clutch or brakecylinder hydraulic fluid chamber just before such the chamber will befilled with it, in the step, a clutch or brake engagement start commandis inputted to a controller, which operates to output a large amountinflow command current to the proportional solenoid of the hydraulicfluid pressure control valve for a predetermined period, so that thedrain of the pilot fluid drained from the pressure proportional valve toa tank is interrupted to allow the pilot fluid pressure in the pilotpressure receiving chamber to be increased to a high level, whereby acommunicating port between the input port and the output port of thepressure control valve becomes large; the second step for flowing asmall amount of hydraulic fluid into the clutch or brake cylinderhydraulic fluid chamber until such the chamber will be filled with it,in the step, after the predetermined period in which the large amountinflow command has been outputted, the controller operates to output asmall amount inflow command current to the proportional solenoid of thehydraulic fluid pressure control valve, so that the pilot fluid drainedfrom the pressure proportional valve is drained to the tank through athrottle to allow the pilot fluid pressure in the pilot pressurereceiving chamber to be lowered, whereby the communicating port betweenthe input port and the output port of the pressure control valve becomessmall; the third step for detecting the termination of filling, in thestep, when the clutch or brake cylinder hydraulic fluid chamber has beenfilled with the hydraulic fluid and the clutch or brake initialengagement pressure rises, the pressure sensor provided at the hydraulicfluid pressure control valve detects the rising of the clutch or brakeinitial engagement pressure and outputs it to the controller; the forthstep for gradually-increasing the clutch or brake cylinder initialengagement hydraulic fluid pressure, in the step, the controller, whichhas been inputted the termination of filling, operates to stopoutputting the small amount inflow command current to the proportionalsolenoid of the hydraulic pressure control valve and then to supply agradually-increasing command current to the solenoid for a predeterminedperiod, so that the clutch or brake initial engagement hydraulic fluidpressure reaches a set pressure for such the predetermined period,whereby the opening size of the throttle, through which the pilot fluidis drained from the pressure proportional valve to the tank, isgradually decreased to allow the pilot fluid pressure in the pilotpressure receiving chamber to be gradually increased, and the pressurein the clutch or brake cylinder inner pressure feedback chamber of thepressure control valve to be increased to balance with such thegradually-increased pilot fluid pressure; and, the fifth step foroutputting the set pressure command signal to the proportional solenoidof the hydraulic fluid pressure control valve, in the step, after suchthe predetermined period in which the clutch or brake initial engagementhydraulic fluid pressure is being increased, the controller operates tostop the hydraulic fluid pressure gradually-increasing command current,and to keep the clutch or brake engagement set pressure, in which thegradually-increasing of the pressure has been finished, the setpressure.